JP2927494B2 - Image signal pulse forming device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal pulse forming apparatus of a laser scanning type image forming apparatus.

[Conventional technology]

Personal computer, EWS (engineering work station), document creation device, digital copier,
There is an image forming apparatus as an external or built-in output device for OA equipment such as a high-speed facsimile.

As an image forming apparatus that responds to the improvement of the processing speed of the OA equipment, that is, the host machine, and the demand for high-quality images as described above, a laser scanning image forming apparatus having excellent printing speed and resolution, such as a laser printer (also known as a laser beam printer). Use) is increasing.

Such laser printers not only form characters and line drawings (two-tone images), but also perform multi-tone images such as photographs and paintings by an area gradation method utilizing the high resolution. It is also used to form

In addition, the character size is not limited to a fixed size determined by the font, and is often used after being enlarged or reduced by editing.

In such enlarged or reduced characters, especially enlarged characters, or dots composed of a set of pixels formed by the area gradation method, disturbances (jaggies) occurring at the black-and-white boundary portion are particularly affected from horizontal and vertical directions. There is a problem that the image quality of the entire image is significantly impaired because it is conspicuous in a slightly inclined direction or near a horizontal portion of the arc.

As shown in FIG. 12, a pulse width control circuit 92 is provided immediately before an LD driver 91 for driving a laser diode (hereinafter, referred to as “LD”) 90 to perform smoothing in order to make such disturbance less noticeable. Atsuta.

That is, the pulse width control circuit 92 divides the entire pulse width of one pixel (hereinafter, simply referred to as “full pulse width”) into n, and according to the data of the target pixel in units of 1 / n of the entire pulse width, or The pulse width is controlled with reference to the data of the left and right (front and back) or surrounding pixels.

[Problems to be solved by the invention]

However, for example, when n = 8, that is, when the pulse width is divided into eight, the conventional pulse width control circuit 92 outputs 0h of a no pulse (h indicates a hexadecimal number) and a full width of 8h of a pulse pattern example shown in FIG. Except for 1h to 7 of the tip pulse group
h or the pulse width control of any one of 9h to Fh of the rear end pulse group.

Therefore, there are cases where the smoothing is performed effectively and cases where the smoothing is not performed, which is not always satisfactory.

The present invention has been made in view of the above points, and has as its object to provide a pulse forming apparatus for an image signal capable of performing effective smoothing in any case.

[Means for solving the problem]

In order to achieve the above object, the present invention provides a laser scanning type image forming apparatus that forms an image by scanning a laser beam modulated according to an image signal. The pulse forming apparatus to be formed is configured as follows.

That is, a pulse that becomes “H” and a pulse that becomes “L” in the full width of a pulse for one pixel, and a plurality of types of pulses that become “H” at the leading end and “L” at the trailing end of the full width of the pulse. ,
A plurality of types of pulses that are "L" at the leading end of the pulse width and "H" at the trailing end, and "L" at the leading and trailing end of the pulse width and become "H" at the middle part Pattern forming means for generating a plurality of different types of pulses, combining the respective pulses and a plurality of the pulses to form a number of different patterns of pulses for one pixel, a target pixel and at least the Left and right or up and down 2
A pattern code converting unit that determines an optimal pattern by referring to data of surrounding pixels including the pixel, and outputs the pattern code; and the pattern forming unit according to the pattern code output by the pattern code converting unit. Pattern selecting means for selecting any one of a large number of different patterns of the formed pulses for one pixel and outputting the selected signal as the image signal.

(Operation)

According to the image signal pulse forming device configured as described above, the pattern code conversion unit performs the image processing according to the data of the target pixel and the surrounding pixels including at least two pixels on the left, right, upper and lower sides. , An optimum pattern is determined, and the pattern code is output.

On the other hand, the pattern forming means includes a pulse that becomes “H” and a pulse that becomes “L” in the entire pulse width of one pixel, and a plurality of types of pulses that become “H” at the leading end and “L” at the trailing end. When,
Generates multiple types of pulses that are “L” at the front end and “H” at the rear end, and multiple types of pulses that are “L” at the front and rear ends and “H” at the middle Then, each of those pulses and a plurality of them are combined to form a number of different patterns of pulses for one pixel.

Then, the pattern selection means selects a pattern that matches the pattern code output by the pattern code conversion means from among the various patterns formed by the pattern formation means, and outputs the selected pattern as an image signal.

Therefore, effective smoothing can be performed in any case, and the frequency of appearance of high-frequency components decreases on average.

〔Example〕

Hereinafter, an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 2 is a schematic configuration diagram showing an internal mechanism of the laser printer according to one embodiment of the present invention.

The photoreceptor belt 10 rotates counterclockwise as indicated by the arrow.
A charging charger 11, a writing unit 12, a developing unit 13, a transfer charging unit 14, and a cleaning unit 15 are arranged in the order of their rotations.

The photoreceptor belt 10 is first uniformly charged on its surface by a charging charger 11, and is then main-scanned by a spot on which a beam modulated by an image signal from the writing unit 12 and deflected in the main scanning direction forms an image. , An electrostatic latent image is formed.

The electrostatic latent image is developed by a developing unit 13 and converted into a visualized toner image, and the toner image is transferred to a sheet 16 conveyed by a transfer charger 14.

The toner and the charge remaining on the photoreceptor belt 10 are removed by the cleaning unit 15, and the removed toner is collected by the cleaning unit 15.

The paper 16 is fed by a paper feed roller 19 from a paper stack 18 on a paper feed cassette 17, abuts against a pair of registration rollers 20, temporarily stops, and is then written by a writing unit 12 to a photosensitive belt 10. The toner image is transferred by the registration roller pair 20 to the transfer charger 14 at a timing corresponding to the above image.

The paper 16 onto which the toner image has been transferred is conveyed by a fixing unit 21, pressed against a fixing roller 21b heated by a pressure roller 21a, and is fixed by the heat and pressure. Is discharged.

FIG. 3 is a perspective view of an essential part showing an example of the writing unit 12. As shown in FIG.

The writing unit 12 is a rotary deflector including an LD (laser diode) unit 30, a first mirror 31, a first cylinder lens 32, a scanner motor 33, and a polygon mirror 34 that is driven to rotate in the direction of arrow A by the scanner motor 33. 35 and fθ lens
36, a second mirror 37, and a second cylinder lens 38.

The LD unit 30 integrates a laser diode (hereinafter referred to as “LD”), a collimator lens that converts a divergent beam emitted from the LD into a parallel light beam, and an aperture that regulates the beam thickness. It is a built-in one.

The parallel light beam emitted from the LD unit 30 is reflected by the first mirror 31 and enters the first cylinder lens 32.

The first cylinder lens 32 forms an image of the incident component of the parallel light beam in the sub-scanning direction on the reflection surface 34 a of the polygon mirror 34.

The beam reflected by the polygon mirror 34 and repeatedly deflected in the main scanning direction forms an image on the surface of the photoreceptor belt 10 in which the main scanning direction component parallelized by the fθ lens 36 moves in the direction of arrow B. After being refracted by the second mirror
The light is reflected at 37 and passes through the second cylinder lens 38 to reach the photoreceptor belt 1.

The second cylinder lens 38 forms an image of the component of the transmitted beam in the sub-scanning direction on the photoreceptor belt 10, so that the beam forms an image on a spot and moves on the main scanning line 10a of the photoreceptor belt 10 in the direction of arrow C. Main scanning.

FIG. 4 is a block diagram showing an example of the control unit of the laser printer.

The controller 40 includes a main microcomputer (hereinafter referred to as “MPU”) 41 and a ROM 4 storing programs, constant data, character fonts, and the like required by the MPU 41.
2 and R to store temporary data, dot patterns, etc.
AM43 and I / O44 that controls input and output of commands and data
And an operation panel 45 connected to the MPU 41 via the I / O 44
And an internal interface (I / F) 46, which are connected to each other by a data bus, an address bus and the like.

A host machine 48 that outputs a print command, character data, and image data is also connected to the MPU 41 via the I / O 44.

The engine driver 50 includes a sub-microcomputer (hereinafter referred to as “CPU”) 51, a ROM 52 storing programs and constant data required by the CPU 51, a RAM 53 storing temporary data, and a data input / output. I control
/ O54 and are connected to each other by a data bus, an address bus and the like.

The I / O 54 is connected to the internal interface 46 of the controller 40, and receives a code signal or an operation panel signal from the controller 40.
Input the status of various switches on 45, and send status signals such as image clock and paper end to the controller 40.
Output to

The I / O 54 is also connected to the writing unit 12 and other sequence device groups 56 constituting the printer engine 55 as printing means, and various sensors 57 including a synchronous sensor.

The controller 40 receives the print command from the host machine 48 by receiving the character code and the image data, edits the character code and the image data, and converts the character code and the image data into a pattern code necessary for writing an image as described later. Is stored in a predetermined area in the RAM 43.

When the image clock is input together with the ready signal from the engine driver 50, the controller 40 converts the pattern code stored in the predetermined area into a code signal synchronized with the image clock in a serial or parallel manner through the internal interface 46 through the engine driver 50. Output to

The engine driver 50 controls the writing unit 12 and the sequence device group 56 of the printer engine 55 based on data from the controller 40, and inputs a code signal required for image writing from the controller 40 to select a corresponding pattern. In addition to outputting to the writing unit 12 as an image signal, a signal indicating the state of each part of the engine is input and processed from the synchronous sensor and other sensors 57, and necessary information and an error signal are output to the controller 40.

FIG. 1 is a block diagram showing a configuration of a pulse forming apparatus according to one embodiment of the present invention.

The pulse forming apparatus 1 includes a pattern forming circuit 2 as a pattern forming unit, an MPU 41 of a controller 40 as a pattern code converting unit, and a selector 3 as a pattern selecting unit.

The MPU 41 is connected to the ROM 42, the RAM 43, and the host machine 48,
As already explained partially (in FIG. 4), the host machine 48
The multi-tone image data consisting of two-tone image data such as a character code or a line drawing or two-tone image data such as a photograph, which indicates the type of character to be input, is stored in the RAM 43 once.

Among the stored data, the character code is developed into a bitmap by a character font consisting of a bitmap font or a vector font stored in the ROM 42. Is converted into dots having different sizes, each of which is a set of pixels by the image processing described above, and these bit maps are stored again in the VRAM (video RAM) area of the RAM 43.

A general printer writes the bit map in the VRAM area directly as a video signal which is an image signal.
Is output to the LD driver 4.

However, when performing smoothing, MPU4
1 performs image processing such as smoothing processing on each pixel constituting a bit map in the VRAM area to convert it into a pattern code, and stores the pattern code in a predetermined area in the RAM 43.

A simple smoothing process is a 3 × 3 matrix including a target pixel and three pixels including left, right, upper and lower two pixels, a cross-shaped pixel including left, right, upper and lower pixels, or all adjacent pixels. There are various types up to 9 pixels and other complicated ones.
The optimum pattern for the target pixel is determined in units of 1 / n of the entire pulse width, the code is determined, and the code is stored in a predetermined area of the RAM 43.

When printing, an engine driver (not shown)
In synchronization with the image clock input from 50, the MPU 41
And outputs the pattern code stored in a predetermined area in the selector 3 to the selector 3.

The selector 3 is connected to the pattern forming circuit 2 and selects a pattern that matches a pattern code input from the MPU 41 among various patterns formed by the pattern forming circuit 2.
The signal is output to the LD driver 4 as an image signal.

The LD driver 4 is connected to an LD 5 which is a laser light source integrally formed with each other, and a photodiode 6 which receives a part of the laser output of the LD 5 and monitors the output, and
A drive current that is turned on / off in accordance with an image signal is output to drive 5, and a monitor current is input from the photodiode 6 to control the drive current so that the laser output of the LD 5 always keeps a constant value. ing.

FIG. 5 is a circuit diagram showing an example of the pattern forming circuit 2 together with the selector 3. FIG.
7 is a timing chart for explaining an example of forming a pattern which is output to the selector 3. FIG. 7 is a waveform diagram illustrating a part of a combination of the formed pattern and its code (hexadecimal number).

The pattern forming circuit 2 shown in FIG. 5 includes a 1/2 frequency divider 61 composed of D-flip flops, two delay circuits 62 and 63, two pattern (P) synthesizing circuits 64 and 65, respectively, and an MPX
And a switch circuit 66 composed of

The 1/2 frequency divider 61 inverts at the rising edge of the image clock WCLK, and has a period twice that of the image clock from the output terminals Q and / Q ("/" means inversion; the same applies to the following description). Pulses having different polarities, that is, pulses having a phase difference of 180 °
2, and the output from the output terminal Q is input to the switch circuit 66 as a switching signal.

Accordingly, the pulses output from the output terminals Q and / Q each have the “H” period corresponding to the entire pulse width, and the delay circuit 6
2, 63 is a pulse PD0 and pulses PD1 to PD7 each of which is composed of an input pulse and a pulse group delayed by 1/8 of the entire pulse width.
Are output to the pattern synthesis circuits 64 and 65, respectively.

Of the pulses shown in FIG. 6, (A) to (H) show PD0 to PD7, respectively, and FIGS. (I) to (K) show / PD5 to / PD7, respectively.

The pattern synthesizing circuits 64 and 65 are each composed of a group of logic circuits, and take the notes of the input pulses PD0 to PD7 to / PD0 to / P
After forming D7, the pulses PD0 to PD7, / PD0 to / PD
7 is logically operated, and its code (h in the description) is shown in FIG.
To indicate that it is a hexadecimal number), and various types of patterns, some of which are exemplified, are synthesized.
Respectively.

The switch circuit 66 displays each pattern output from the pattern synthesizing circuit 64 when the switching signal input from the output terminal Q of the 1/2 frequency divider 61 is "H", and the pattern synthesizing circuit when the switching signal is "L". Each pattern output by 65 is switched and output to the selector 3.

Therefore, the switch circuit 66 is connected to the pattern synthesis circuits 64, 6
Each pattern obtained by alternately switching the patterns of pixels adjacent to each other output from 5 is a pattern obtained by ANDing the pulse PD0.

The selector 3 is provided with the pattern forming circuit 2 as described above.
A pattern corresponding to the pattern code input from the MPU 41 (FIG. 1) is selected from various patterns synchronized with the image clock WCLK input from the switch circuit 66, and output to the LD driver 4 as an image signal (video signal). I do.

The pulses shown in FIGS. 6 (L)-(N) are PD3 and / PD
5, having patterns synthesized by AND of PD2 and / PD6, and PD1 and / PD7, and 10h, 11h, and 12h shown in FIG. 7, respectively.
Is a part of the pulse group generated in the intermediate part corresponding to

The pulse group generated in the middle part is not limited to the centrally symmetric type such as 10h to 12h illustrated, but the leading and trailing ends of the entire pulse width are “L” and one “H” portion Are included.

0h and 8h shown in FIG. 7 need only select the earth line and the pull-up line without outputting the pattern synthesizing circuits 64 and 65, and the leading edge pulse group 1h to 7h and the trailing edge pulse group can be selected. In 9h to Fh, if the pattern synthesizing circuits 64 and 65 output / PD1 to / PD7 and PD7 to PD1, respectively, as they are, the selector 3 makes an AND with PD0 to create a pattern.

Patterns after 13h are synthesized by the pattern synthesizing circuits 64 and 65 by combining the appropriate patterns in the leading edge pulse group, the trailing edge pulse group, and the intermediate pulse group to form an OR.

Among the patterns exemplified in FIG. 7, a part of the full width pulse 8h and 9h to Fh, 13h to 27h,
The pattern such as 2Bh to 32h is an image signal output from the selector 3 when combined with the subsequent full width pulse 8h and the pattern such as 1h to 7h, 13h to 2Ah, and 2Eh to 32h whose leading end is "H". In this case, a continuous pattern between pixels is formed, and a pattern having a pulse width longer than the entire pulse width of one pixel is often formed by a combination thereof.

Therefore, as compared with the case where the whole pulse width of one pixel is not divided into n parts, the frequency band is increased by n times in the high frequency range, but the whole pulse width is divided into n parts only by the leading edge pulse group or the trailing edge pulse group. In comparison with the conventional example in which smoothing is performed, the frequency of appearance of high-frequency components is reduced on average.

Hereinafter, the effect of the smoothing according to the present invention will be described with reference to a sample shown in FIG.

FIG. 8 shows an example of a "W uppercase letter" consisting of 22 × 28 dots vertically and horizontally, and one cell corresponds to one pixel.

FIG. 9 and FIG. 10 each show the "W" shown in FIG.
9 shows the bit map thereof, and FIG. 10 shows an enlarged view of the formed image. In both figures, (A) shows the smoothing by the pulse width division of the pixel. If not performed, (B) and (C) show the case where smoothing is performed by dividing the entire pulse width into eight, respectively.
(B) is an example composed of only the conventional tip pulse group, and (C) is an example composed of the pattern according to the present invention.

In the bit map shown in FIG. 9, FIG. 9A is formed by binarized data, and FIGS. 9B and 9C are formed by codes indicating the respective patterns of FIG.

As is clear from the results shown in FIG. 10, the effect is shown on the right side of the hatched black portion in FIG. 10B with the conventional smoothing, compared to FIG. However, the left side is the same as FIG.

In the example shown in FIG. 2C according to the present invention, both sides of the shaded black portion are both smoothed, so that it is visually smooth, and the effect is remarkable especially in the concave portions seen in the upper left and the center. .

In the example shown in FIGS. 8 to 10, a pattern consisting of a pulse group at the leading end and the trailing end is used. However, the pulse group at 10h to 12h and the similar intermediate part shown in FIG. It is used for the upper and lower outer contours of the black line of “0” where the upper and lower ends appear, for example.

In particular, in the case of a multi-tone image in which dots as a set of pixels are formed by binarization processing such as a dither method, smoothing is easy and disordered because the center position (coordinates) of the formed dots is known. In addition to obtaining a dot with a small number of dots, it is also possible to perform image processing for obtaining an image excellent in gradation because gradation can be expressed more finely than that obtained by ordinary binarization processing.

In the case of forming a multi-tone image having a relatively small number of tones, a binarization process simpler than the dither method is often performed with a set of a small number of pixels.

FIG. 11 is a partially enlarged view showing an example in which a multi-tone image is formed by a set of 4 pixels of 2 × 2. FIG. 11A shows a case where pulse width division is not performed. C) The total pulse width is 4
(B) shows a case composed of only the pulse group at the tip, and (C) shows a case composed of the pattern according to the present invention.
9A and 9B, the numbers of divisions are different in FIGS.
(A)-(C) respectively correspond.

FIGS. 11 (A) to 11 (C) show darkening in the direction from top to bottom, and FIGS. 11 (B) and 11 (C) show finer darkening from left to right.

Although FIG. 11 (A) can express only 5 gradations, that is, 4 gradations including white blank, FIGS. 11 (B) and 11 (C) show 16 gradations with the same number of pixels due to the effect of the pulse width divided by 4. The difference can be expressed.

Further, FIG. 11 (C) according to the present invention is formed because the white and black areas are almost evenly dispersed within the area of 4 pixels as compared with FIG. 11 (B) based on the conventional pattern. There is also the effect that the image looks smooth.

As described above, an example in which the present invention is applied to a laser printer has been described.
It goes without saying that the present invention can be applied to a laser scanning type image forming apparatus built in OA equipment.

Further, the photoreceptor may be not only an electrophotographic method such as an OPC (organic photoreceptor), but also a silver salt photoreceptor such as a photographic film used for printing plate making.

〔The invention's effect〕

As described above, the pulse forming apparatus for image signals of the laser scanning type image forming apparatus according to the present invention can perform effective smoothing in any case.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration example of a pulse forming apparatus according to the present invention, FIG. 2 is a schematic configuration diagram of an internal mechanism of a laser printer showing one embodiment of the present invention, and FIG. FIG. 4 is a block diagram showing an example of the control unit, FIG. 5 is a circuit diagram showing an example of the pattern forming circuit, and FIG. 6 is a diagram for explaining an example of the pattern formation. FIG. 7 is a waveform diagram illustrating a part of the formed pattern together with its code, FIG. 8 is also a dot pattern of a sample character of the smoothing, and FIGS. 9 and 10 are also a sample of the sample. FIG. 11 is an enlarged view of a bit pattern and a dot pattern showing a character portion, FIG. 11 is an enlarged view of a dot pattern showing the gradation, and FIG. 12 is a conventional example of a pulse forming apparatus. It is a block diagram. DESCRIPTION OF SYMBOLS 1 ... Pulse forming apparatus 2 ... Pattern forming circuit (pattern forming means) 3 ... Selector (pattern selecting means) 4 ... LD driver 5 ... LD (laser diode) 40 ... Controller 41 ... MPU (microcomputer) ; Pattern code conversion means)

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masumi Sato 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Company, Ltd. (72) Inventor Tomoatsu Imamura 1-3-6 Nakamagome, Ota-ku, Tokyo No. Ricoh Co., Ltd. (56) References JP-A-61-214666 (JP, A) JP-A-63-179748 (JP, A) JP-A-1-244858 (JP, A) JP-A-3-33769 (JP, A) (58) Field surveyed (Int. Cl. ⁶ , DB name) B41J 2/44 B41J 2/485

Claims (1)

(57) [Claims] 1. A pulse forming apparatus for forming a pulse of an image signal according to each pixel data of a laser scanning type image forming apparatus which forms an image by scanning a laser beam modulated according to an image signal. A pulse that becomes “H” and a pulse that becomes “L” with a full width of one pixel, a plurality of types of pulses that become “H” at a leading end of the full width of the pulse and “L” at a trailing end thereof, Multiple types of pulses that are "L" at the leading end of the pulse width and "H" at the trailing end, and "L" at the leading and trailing ends of the pulse and "H" at the middle A pattern forming means for generating a plurality of kinds of pulses, synthesizing each of the pulses and a plurality of the pulses to form a number of different patterns of a pulse for one pixel, Or the surrounding area including the upper and lower pixels Pattern code converting means for determining an optimal pattern by referring to raw data and outputting the pattern code; and for one pixel formed by the pattern forming means in accordance with the pattern code output by the pattern code converting means. A pattern selecting means for selecting any one of a number of different patterns of the pulse and outputting the selected signal as the image signal.